Free man could be charged again: WA police

A man who spent almost two years behind bars awaiting trial before having drug charges against him dropped could be re-charged, the state's police commissioner says.

Antonio Amabile was charged with possessing four kilograms of meth, which was found at his apartment in February 2015, but a judge ruled that DNA evidence was inadmissible because police may have contaminated it.

WA Police Commissioner Karl O'Callaghan said a peer review would determine what went wrong, adding the case could be "re-continued" if there is sufficient other evidence.

"It would be different if he was acquitted by a jury," he told 6PR radio on Thursday.